Expandable mandrels for the support of printing cylinders are known from U.S. Pat. No. 4,381,709 issued May 3, 1983 to the present inventors. Such mandrels include spaced cylindrical journal members for the printing cylinder, and expandable diaphragm-like sleeves provided on the external periphery of the respective journal members, and which can be expanded radially outwardly by hydraulic actuators into gripping and supporting relationship with the interior of a printing cylinder. The respective journal members are held in fixed axially spaced relationship by an interconnecting sleeve, which is pinned to the respective journal members.
While this prior proposed arrangement is admirable in providing rigid and concentric support for a printing cylinder, it is limited in its use to the support of cylinders of only one selected internal diameter. Should it be required that a printing cylinder of a different diameter be used in the rotary press, then, it is necessary to remove the entire expandable mandrel assembly from the press and to substitute therefore a replacement mandrel assembly having a diameter appropriate to the internal diameter of the printing cylinder of larger diameter to be employed. This operation not only is time consuming with the consequential expense of down-time of the press, but also requires that a range of mandrel assemblies appropriate to the expected range of printing cylinder diameters be available at the site of the printing press, with the consequential expense of providing a multiplicity of mandrels of different diameters, and, the expense entailed in the required storage of those mandrels that are not in use.
This problem is overcome to the greatest possible extent by the provision of annular hydraulically actuated journals having expandable members at their inner and outer peripheries, and which can be hydraulically locked to a central shaft, as is taught by the present applicants in U.S. Ser. No. 593,952 filed Mar. 27, 1984, now U.S. Pat. No. 4,624,184. However, this concept cannot be employed where expandable mandrels are the only ones available to the printer, in that such mandrels are devoid of a central shaft.